Two-Dimensional Imaging of Permittivity Distribution by an Activated Meta-Structure with a Functional Scanning Defect

Simple, Fast, and Accurate Broadband Complex Permittivity Characterization Algorithm: Methodology and Experimental Validation from 140 GHz up to 220 GHz

Accurate permittivity characterization has attracted a lot of attention in various areas. Resonant characterization methods are well-known for their accuracy, but they are restricted in very narrow frequency ranges, and thus, they are normally not recommended to be used for dispersive or high-loss materials. Transmission line characterization techniques are outstanding for being inexpensive, accurate, and broadband, but the algorithms are often complex to perform. This paper proposes a fast, simple, and accurate broadband permittivity characterization algorithm, which is mainly suitable for millimeter-wave applications. It combines a general line–line method and a closed-form algorithm, extracting the complex permittivity of the material under test (MUT) without the need for calculating any intermediate parameters. Validation measurements on de-ionized water in the frequency range from 140 to 220 GHz are in very good agreement with the literature data, which successfully indicates that the proposed algorithm is reliable and accurate for millimeter wave permittivity characterization.

Analysis and observation of the breakdown of Babinet’s principle in complementary spoof surface plasmon polariton structures

A metal plate array (MPA) which is a structure complimentary to a metal hole array (MHA), supports spoof surface plasmon polaritons (SSPP) as well as an MHA does. Babinet’s principle attributes the phenomenon of duality to transmission characteristics of the complimentary impedance surfaces because of the symmetry of the behaviors of electric and magnetic fields. However, it is also a fact that the complimentary structures do not follow this principle if they have wavelength-size thickness, because electromagnetic waves do not treat such thick structures as a boundary surface but as propagation spaces with the specific boundaries such as a waveguide which shows SSPP modes. If the thickness is so small that it is negligible, Babinet’s principle is still valid, while it has been uncertain how the layer thickness works to break the principle as it is increased. The unconfirmed transformation is revealed analytically and experimentally with the use of MPAs and MHAs of varying thicknesses.

Dynamic Modulation Band Rejection Filter Based on Spoof Surface Plasmon Polaritons

In this paper, we proposed a dynamic modulation band rejection filter based on the spoof surface plasmon polaritons (SSPPs) waveguide. The dynamic adjusting mainly derives from changing the capacitance between the U-shape and the waveguide configuration. The capacitance can modulate the cut-off frequency of fundamental mode. The rejection band is formed by the high order propagation mode and the cut-off frequency of fundamental mode. We analyzed the dispersion curve and transmission performance of the band rejection filter with different capacitances. Compared with the previous scheme, the design we proposed here has a simpler and more delicate configuration to process and decreases the mechanical error. We experimentally demonstrated the excellent performance of the device by changing the direct voltage loaded on the varactor diode and achieved real time modulation around 2 GHz.